Why Your Furnace Has a Strange Smell

As the weather cools down and you swap from cooling to heating your home, some homeowners are worried about weird furnace smells in the air. Learn what the most common furnace smells mean and how proactive you should be about them.

The Furnace Smells Musty

Musty furnace smells usually indicate mold growth hiding in the HVAC system. To avoid exposing your family to allergy-inducing mold, handle this problem as quickly as possible.

A clogged air filter can harbor mold, so getting rid of the smell can be as straightforward as replacing the filter. If that fails to remove the smell, the AC evaporator coil mounted near the furnace may be to blame. This component accumulates condensation, which could stimulate mold growth. You'll be better off with a professional’s help to examine and clean the evaporator coil. When this still doesn't help, consider requesting air duct cleaning. This service eliminates hidden mold, no matter where it’s growing in your air ducts.

The Furnace Smells Like Spoiled Eggs

This is one of the most concerning furnace smells because it frequently suggests a gas leak. The utility company puts in a particular substance called mercaptan to the natural gas supply to make leaks easier to notice.

If you detect a rotten egg smell close to your furnace or originating from your ductwork, shut down the heater straightaway. If you remember where the main gas supply valve is, shut that off as well. Then, evacuate your home and dial 911, in addition to your gas company. Don’t reenter the house until a professional tells you it’s safe.

The Furnace Has a Sour Stench

If you notice a sour smell that stings your nose while close to the furnace, this may mean the heat exchanger cracked open. This vital component contains combustion fumes, such as carbon monoxide, so a cracked heat exchanger could allow unsafe levels of CO gas into your home.

Carbon monoxide poisoning has the potential to be fatal, so switch off your furnace immediately if you recognize a sour odor. Then, reach out to an HVAC professional for an inspection. Consider replacing your furnace if a cracked heat exchanger is to blame. For your continued safety going forward, ensure you have functional CO detectors on all floors of your home.

The Furnace Smells Dusty

When you fire up the furnace for the first time each fall, you probably expect a dusty odor to appear for a little while. This is the smell of six months’ worth of dust burning away as the furnace wakes up. As long as the smell disperses within one day, you don't have anything to worry about.

The Furnace Has a Smoky Smell

Natural gas, oil and propane furnaces are combustion appliances, so they vent fumes safely out of your home. A smoky smell can mean the flue is clogged, and now fumes are backdrafting into your home. The odor may permeate the entire house, endangering your family’s health if you let it continue. So turn off the furnace and call a professional as soon as you can to request furnace repair.

The Furnace Smells Like It's Burning Plastic

Overheating and melted electrical components are the most common reason for a burning plastic smell to appear. A malfunctioning fan motor is another possibility. If you don’t tackle the problem, an electrical fire may start, or your furnace could experience irreparable damage. Disable the heating system as soon as possible and call an HVAC technician for help diagnosing and repairing this weird furnace smell.

The Furnace Has an Oily Smell

If you use an oil furnace, you might detect this smell when the oil filter becomes clogged. Try replacing it to see if that addresses the problem. If the smell persists for more than a day after carrying out this step, it may suggest an oil leak. You'll be better off with help from an HVAC expert to handle this problem.

The Furnace Reeks of Sewer Odors

Sewer gas smells quite similar to rotting eggs, so first rule out the likelihood of a natural gas leak. If that’s not the issue, your sewer lines might have an issue, for example a dry trap or sewer leak. Pour water down the drains, including the basement floor drain, to fill dry sewer traps. If the smell sticks around, you’ll need to contact a sewer line repair company.

Contact Service Experts Heating & Air Conditioning for Furnace Repair

When in doubt, get in touch with an HVAC technician to assess and repair your furnace. At Service Experts Heating & Air Conditioning, we deliver thorough diagnostic services to identify the problem before we figure out the best solution. Then, we suggest the most viable, cost-effective repairs, alongside an up-front estimate for every option. Our ACE-certified technicians can resolve just about any heating problem, and we back our work with a 100% satisfaction guarantee for one year. To ask questions about why your furnace smells bad or to request furnace repair near you, please contact your local Service Experts Heating & Air Conditioning office today.